Large-area selective ablation systems and methods

ABSTRACT

A method ( 200 ) of using a laser ablation system ( 100 ) to clean an area ( 130 ) of a surface ( 128 ) with a laser beam ( 120 ), having a target fluence and a target irradiance. The area ( 130 ) comprises scan regions ( 136 ), each having a scan width ( 140 ). The method ( 200 ) comprises determining a traverse scan speed, a laser-beam average power, a laser pulse repetition rate, a laser pulse width, and a laser-beam spot area of the laser beam ( 120 ) for each one of the scan regions ( 136 ) to achieve the target fluence and the target irradiance. The scan width ( 140 ) of at least one of the scan regions ( 136 ) is different from the scan width ( 140 ) of another one of the scan regions ( 136 ). The method ( 200 ) also comprises sequentially scanning, across the scan width ( 140 ), each one of the scan regions ( 136 ) of the area ( 130 ) with the laser beam ( 120 ) at the target fluence and the target irradiance.

TECHNICAL FIELD

The present disclosure relates to large-area selective ablation systemsand methods.

BACKGROUND

Laser ablation is a method to clean or refresh surfaces. Contaminants orsurface layers are ablated (destroyed) by applying laser energy directlyto the surface. The laser is tuned to ablate the contaminants or surfacelayers while leaving the underlying surface material intact. Theeffectiveness of laser ablation is substantially due to the laser energyabsorbed at the surface. If too much energy is absorbed, the surface maybe damaged (over ablated). If too little energy is absorbed, thecontaminants or surface layers may not be sufficiently affected (underablated).

In conventional laser ablation, the laser beam is scanned across thesurface in a raster fashion. The laser beam is scanned quickly in onedirection (the scan direction) and relatively slowly in anotherdirection (the traverse direction). The laser beam generally is scannedso quickly in the scan direction that the laser appears, and may betreated, as a laser sheet. Generally, laser ablation is performed byscanning a rectangular area with the width and breadth corresponding tothe scan and traverse directions. The laser sheet in the scan directionis swept in the traverse direction at a traverse scan speed to cover thearea to be ablated.

The effectiveness of laser ablation is determined by the irradiance(surface density of laser power) and fluence (surface density ofaccumulated laser energy), among other factors such as laser wavelength,surface material, and material to be ablated. For conventional laserablation, the laser power is constant during ablation and the irradianceand fluence are substantially constant because the ablation area isrectangular with a constant scan width. If the scan width is changed,the irradiance and/or the fluence is changed. For example, a differentscan width leads to a different width of the laser sheet and a differentirradiance for the laser sheet (because the same laser power is spreadover a different scan width). Hence, conventional laser ablation suffersfrom being restricted to rectangular areas (with a constant scan width),over ablation (due to exposing more area than necessary or exposing anarea for too long), and/or under ablation (due to exposing an area fortoo little time).

SUMMARY

Accordingly, apparatuses and methods, intended to address at least theabove-identified concerns, would find utility.

The following is a non-exhaustive list of examples, which may or may notbe claimed, of the subject matter according to the invention.

One example of the subject matter according to the invention relates toa laser ablation system. The laser ablation system comprises a laser, ascanning head, a laser-positioning apparatus, and a controller. Thelaser is configured to emit a laser beam. The scanning head isconfigured to deliver the laser beam, emitted by the laser, onto asurface. The laser-positioning apparatus is configured to adjustrelative positions of the surface and the scanning head. The controlleris programmed to determine operation parameters and to scan the surface.The controller is programmed to determine operation parameters such as atraverse scan speed, a laser-beam average power, a laser pulserepetition rate, a laser pulse width, and a laser-beam spot area foreach one of scan regions of an area of the surface. The traverse scanspeed, the laser-beam average power, the laser pulse repetition rate,the laser pulse width, and the laser-beam spot area, corresponding toany one of the scan regions, produce a target fluence and a targetirradiance of the laser beam. The scan regions are arranged so that allof the area of the surface is scannable with the laser beam. Each one ofthe scan regions has a scan width. The scan width of at least one of thescan regions is different from the scan width of another one of the scanregions. The controller is programmed to scan the area of the surfacewith the laser beam at the target fluence and the target irradiance byscanning each one of the scan regions at the traverse scan speed,corresponding to that particular one of the scan regions, and across thescan width, corresponding to that particular one of the scan regions.The laser beam has the laser-beam average power, corresponding to thatparticular one of the scan regions, the laser pulse repetition rate,corresponding to that particular one of the scan regions, the laserpulse width, corresponding to that particular one of the scan regions,and the laser-beam spot area, corresponding to that particular one ofthe scan regions.

Another example of the subject matter according to the invention relatesto a method of using a laser ablation system to clean an area of asurface with a laser beam, having a target fluence and a targetirradiance. The area comprises scan regions, each having a scan width.The method of using the laser ablation system comprises determining atraverse scan speed, a laser-beam average power, a laser pulserepetition rate, a laser pulse width, and a laser-beam spot area of thelaser beam for each one of the scan regions to achieve the targetfluence and the target irradiance of the laser beam when scanning eachone of the scan regions with the laser beam. The scan width of at leastone of the scan regions is different from the scan width of another oneof the scan regions. The method also comprises sequentially scanning,across the scan width, each one of the scan regions of the area with thelaser beam at the target fluence and the target irradiance.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described examples of the present disclosure in generalterms, reference will now be made to the accompanying drawings, whichare not necessarily drawn to scale, and wherein like referencecharacters designate the same or similar parts throughout the severalviews, and wherein:

FIG. 1 is a block diagram of a laser ablation system, according to oneor more examples of the present disclosure;

FIG. 2 is a schematic, perspective view of the laser ablation system ofFIG. 1, cleaning a surface of a workpiece, according to one or moreexamples of the present disclosure;

FIG. 3 is a schematic, top view of a surface of a workpiece indicatingscan regions, according to one or more examples of the presentdisclosure;

FIG. 4 is a block diagram of a method of using the laser ablation systemof FIG. 1 to clean an area of a surface, according to one or moreexamples of the present disclosure;

FIG. 5 is a block diagram of aircraft production and servicemethodology; and

FIG. 6 is a schematic illustration of an aircraft.

DETAILED DESCRIPTION

In FIGS. 1-6, referred to above, solid lines, if any, connecting variouselements and/or components may represent mechanical, electrical, fluid,optical, electromagnetic and other couplings and/or combinationsthereof. As used herein, “coupled” means associated directly as well asindirectly. For example, a member A may be directly associated with amember B, or may be indirectly associated therewith, e.g., via anothermember C. It will be understood that not all relationships among thevarious disclosed elements are necessarily represented. Accordingly,couplings other than those depicted in the block diagrams may alsoexist. Dashed lines, if any, connecting blocks designating the variouselements and/or components represent couplings similar in function andpurpose to those represented by solid lines; however, couplingsrepresented by the dashed lines may either be selectively provided ormay relate to alternative examples of the present disclosure. Likewise,elements and/or components, if any, represented with dashed lines,indicate alternative examples of the present disclosure. One or moreelements shown in solid and/or dashed lines may be omitted from aparticular example without departing from the scope of the presentdisclosure. Environmental elements, if any, are represented with dottedlines. Virtual (imaginary) elements may also be shown for clarity. Thoseskilled in the art will appreciate that some of the features illustratedin FIGS. 1-6 may be combined in various ways without the need to includeother features described in FIGS. 1-6, other drawing figures, and/or theaccompanying disclosure, even though such combination or combinationsare not explicitly illustrated herein. Similarly, additional featuresnot limited to the examples presented, may be combined with some or allof the features shown and described herein.

In FIGS. 4-5, referred to above, the blocks may represent operationsand/or portions thereof and lines connecting the various blocks do notimply any particular order or dependency of the operations or portionsthereof. Blocks represented by dashed lines indicate alternativeoperations and/or portions thereof. Dashed lines, if any, connecting thevarious blocks represent alternative dependencies of the operations orportions thereof. It will be understood that not all dependencies amongthe various disclosed operations are necessarily represented. FIGS. 4-5and the accompanying disclosure describing the operations of themethod(s) set forth herein should not be interpreted as necessarilydetermining a sequence in which the operations are to be performed.Rather, although one illustrative order is indicated, it is to beunderstood that the sequence of the operations may be modified whenappropriate. Accordingly, certain operations may be performed in adifferent order or simultaneously. Additionally, those skilled in theart will appreciate that not all operations described need be performed.

In the following description, numerous specific details are set forth toprovide a thorough understanding of the disclosed concepts, which may bepracticed without some or all of these particulars. In other instances,details of known devices and/or processes have been omitted to avoidunnecessarily obscuring the disclosure. While some concepts will bedescribed in conjunction with specific examples, it will be understoodthat these examples are not intended to be limiting.

Unless otherwise indicated, the terms “first,” “second,” etc. are usedherein merely as labels, and are not intended to impose ordinal,positional, or hierarchical requirements on the items to which theseterms refer. Moreover, reference to, e.g., a “second” item does notrequire or preclude the existence of, e.g., a “first” or lower-numbereditem, and/or, e.g., a “third” or higher-numbered item.

Reference herein to “one example” means that one or more feature,structure, or characteristic described in connection with the example isincluded in at least one implementation. The phrase “one example” invarious places in the specification may or may not be referring to thesame example.

As used herein, a system, apparatus, structure, article, element,component, or hardware “configured to” perform a specified function isindeed capable of performing the specified function without anyalteration, rather than merely having potential to perform the specifiedfunction after further modification. In other words, the system,apparatus, structure, article, element, component, or hardware“configured to” perform a specified function is specifically selected,created, implemented, utilized, programmed, and/or designed for thepurpose of performing the specified function. As used herein,“configured to” denotes existing characteristics of a system, apparatus,structure, article, element, component, or hardware which enable thesystem, apparatus, structure, article, element, component, or hardwareto perform the specified function without further modification. Forpurposes of this disclosure, a system, apparatus, structure, article,element, component, or hardware described as being “configured to”perform a particular function may additionally or alternatively bedescribed as being “adapted to” and/or as being “operative to” performthat function.

Illustrative, non-exhaustive examples, which may or may not be claimed,of the subject matter according the present disclosure are providedbelow.

Referring generally to FIGS. 1-3 and particularly to, e.g., FIG. 1,laser ablation system 100 comprises laser 102, scanning head 104,laser-positioning apparatus 106, and controller 110. Laser 102 isconfigured to emit laser beam 120. Scanning head 104 is configured todeliver laser beam 120, emitted by laser 102, onto surface 128.Laser-positioning apparatus 106 is configured to adjust relativepositions of surface 128 and scanning head 104. Controller 110 isprogrammed to determine operation parameters and to scan surface 128.Controller 110 is programmed to determine operation parameters, such astraverse scan speed, laser-beam average power, laser pulse repetitionrate, laser pulse width, and laser-beam spot area for each one of scanregions 136 of area 130 of surface 128. The traverse scan speed, thelaser-beam average power, the laser pulse repetition rate, the laserpulse width, and the laser-beam spot area, corresponding to any one ofscan regions 136, produce a target fluence and a target irradiance oflaser beam 120. Scan regions 136 are arranged so that all of area 130 ofsurface 128 is scannable with laser beam 120. Each one of scan regions136 has scan width 140. Scan width 140 of at least one of scan regions136 is different from scan width 140 of another one of scan regions 136.Controller 110 is programmed to scan area 130 of surface 128 with laserbeam 120 at the target fluence and the target irradiance by scanningeach one of scan regions 136 at the traverse scan speed, correspondingto that particular one of scan regions 136, and across scan width 140,corresponding to that particular one of scan regions 136. Laser beam 120has the laser-beam average power, corresponding to that particular oneof scan regions 136, the laser pulse repetition rate, corresponding tothat particular one of scan regions 136, the laser pulse width,corresponding to that particular one of scan regions 136, and thelaser-beam spot area, corresponding to that particular one of scanregions 136. The preceding subject matter of this paragraphcharacterizes example 1 of the present disclosure.

Laser ablation system 100 is configured to clean or refresh surface 128by laser ablation with laser beam 120. In conventional laser ablation,the laser is operated with constant operation parameters (e.g.,laser-beam power) and scanned over a rectangular region of the surfaceto be ablated. The laser is scanned in a raster fashion with constantspeed and with each scan line having a constant scan width. If the areaof interest (where ablation is desired) is non-rectangular or irregular,conventional laser ablation will apply too much power and/or energy insome regions, and/or not enough power and/or energy in other regions.For example, FIG. 3 illustrates area 130 of surface 128 that has anon-rectangular form (a stepped triangular shape). For a conventionallaser ablation system to ablate area 130 of the example in FIG. 3, thelaser may be scanned in rectangular region 126 that encompasses area130. The area of rectangular region 126 outside of area 130 receiveslaser power in a conventional system and may be significantly damaged(or merely over ablated) by the unnecessary power. Additionally, thetime to scan the area of rectangular region 126 outside of area 130reduces the efficiency of ablation (adding unnecessary time to the totaltime to ablate area 130).

Further, if a conventional laser ablation system were to scan area 130of FIG. 3 as a series of rectangular regions with differing scan widths140, each different rectangular region would receive a different amountof laser energy and/or power because the laser is scanned in the sameraster fashion at the same speed. More specifically, for a laser beam ofconstant power, the amount of energy deposited on a surface isproportional to the amount of time the laser beam impinges the surface(also referred to as the residence time at the surface). Forconventional laser ablation systems and laser ablation system 100, thelaser beam (e.g., laser beam 120) is raster scanned over the area ofinterest (e.g., area 130) by moving the laser beam in two distinctdirections: scan width direction 144 and traverse direction 146. Thelaser (e.g., laser 102) is scanned relatively quickly in scan widthdirection 144 and relatively slowly in traverse direction 146.Typically, scanning in scan width direction 144 is so rapid that thelaser beam may be considered a laser sheet with a width being the scanwidth (e.g., scan width 140). The power of the laser sheet is the sameas the power of the laser beam but the irradiance (the surface densityof the power, also referred to as the power density) of the laser sheetis reduced from that of the laser beam. The irradiance is inverselyproportional to the width of the laser sheet (scan width). Hence, asmaller scan width produces a larger irradiance and a larger scan widthproduces a smaller irradiance.

The cleaning effectiveness (i.e., the effectiveness of ablation) oflaser ablation is determined by the surface density of laser power andthe surface density of laser energy at surface 128. The surface densityof laser power (laser power divided by surface area receiving thatpower) is known as irradiance. The surface density of laser energy(laser energy divided by surface area receiving that energy) is known asfluence. Other factors, such as laser wavelength, surface material, andmaterial to be ablated, also may affect the cleaning effectiveness.

Laser ablation system 100 is configured to adjust operation parametersfor each of scan regions 136 such that each of scan regions 136 isscanned with the same target fluence and the same target irradiance.Scanning with the same fluence and irradiance provides the same cleaningeffectiveness for each of scan regions 136. In conventional laserablation, the fluence and irradiance are primarily determined by thescan width. If the scan width changes (while the scanning speed remainsconstant), the fluence and/or irradiance are changed because theresidence time of the laser at the surface is adjusted.

Scan regions 136 are arranged within area 130 of surface 128. Surface128 is a surface of workpiece 124 to be cleaned or refreshed by laserablation by laser ablation system 100. Workpiece 124 is a workpiece oflaser ablation system 100 and not necessarily a structure in the processof being formed. Examples of workpiece 124 include a mold, a form, amandrel, a vehicle, a structural component, and elements thereof.Generally, workpiece 124 includes hard and/or resilient materials suchas metal and/or ceramic. Surface 128 may be a substantially metal and/orceramic surface. Workpiece 124 and/or surface 128 may include polymericmaterials, glasses, and/or composite materials. For example, workpiece124 may include carbon fiber-reinforced polymer.

Area 130 of surface 128 is a surface region of surface 128. Area 130 isa contiguous surface region of surface 128 but not necessarily theentirety of surface 128 or the entirety of one or more faces, facets,and/or planes of surface 128. Laser ablation system 100 is configuredspecifically to accommodate non-rectangular area 130. That is, scanregions 136, which are arranged within area 130, do not have scan width140 that is uniform. At least one of scan regions 136 has scan width 140that is different than at least one other of scan regions 136.

Scan regions 136 are each a distinct region of area 130 (scan regions136 may partially overlap). Each of scan regions 136 may be a smallsection of area 130 and may be substantially the area swept by laserbeam 120 in scan width direction 144. Laser beam 120 is directed bylaser ablation system 100 (e.g., by laser-positioning apparatus 106) tomove substantially continuously and sequentially among scan regions 136.Hence, completion of one of scan regions 136 is followed by the start ofanother of scan regions 136. Individual ones of scan regions 136 aredistributed in traverse direction 146.

Laser 102 and laser beam 120 have several characteristics that may beadjusted to control irradiance and fluence in each of scan regions 136.Laser 102 has a temporally modulated output (i.e., the output is pulsedand/or modulated). Laser 102 and may be a pulsed laser (e.g., laser 102may be mode locked, cavity dumped, Q switched, etc.) and/or may includea gate, shutter, chopper, electro-optical cell, an acousto-optical cell,etc. to impose temporal structure in laser beam 120. Laser beam 120 hasa laser-beam average power, a laser pulse repetition rate (fundamentalfrequency of the laser intensity), a laser pulse width, and a laser-beamspot area (the area of laser beam 120 as it impinges surface 128). Thelaser pulse width is the period of time in which the laser intensity issignificant for each repetition period corresponding to the laser pulserepetition rate. For pulsed laser output, the laser pulse width, as usedherein, is the full width of a pulse at half maximum intensity. Laserbeam 120 is swept across scan regions 136, in scan width direction 144,at a raster scan speed (which may be different for different ones ofscan regions 136). Laser beam 120 is swept between scan regions 136, intraverse direction 146, at a traverse scan speed (which may be differentfor different ones of scan regions 136). Each one of the characteristics(traverse scan speed, raster scan speed, laser-beam average power, laserpulse repetition rate, laser pulse width and laser-beam spot area) maybe controlled or adjustable by laser ablation system 100 independentlyfor each of scan regions 136. Some, but not all, of the characteristicsmay be the same for each of scan regions 136. That is, at least one ofthe characteristics is different for at least one of scan regions 136.

For laser ablation system 100, irradiance is a function of thelaser-beam average power and the laser-beam spot area. As used herein,target irradiance specifically refers to peak irradiance, i.e.,laser-beam peak power divided by the surface covered by laser beam 120.Generally, laser-beam peak power is a function of the laser-beam averagepower. Target irradiance may be calculated according to:

$\begin{matrix}{I = \frac{P}{P_{r} \cdot P_{w} \cdot A}} & ( {{Eq}.\mspace{14mu} 1} )\end{matrix}$

where I is target irradiance (peak irradiance), P is laser-beam averagepower, P_(r) is laser pulse repetition rate, P_(w) is laser pulse widthand A is laser-beam spot area. The target irradiance may be increased byincreasing the laser-beam average power, decreasing the laser pulserepetition rate, decreasing the laser pulse width, and/or decreasing thelaser-beam spot area. If the laser-beam average power is decreased, thetarget irradiance may be maintained by compensating decreases(proportional) in the laser pulse repetition rate, the laser pulsewidth, and/or the laser-beam spot area.

For laser ablation system 100, fluence is a function of the laser-beamaverage power, scan width 140, and the traverse scan speed. As usedherein, target fluence specifically refers to fluence of laser beam 120as it is scanned across area 130. Target fluence may be calculatedaccording to:

$\begin{matrix}{F = \frac{P}{S_{w} \cdot T_{s}}} & ( {{Eq}.\mspace{14mu} 2} )\end{matrix}$

where F is target fluence, P is laser-beam average power, S_(w) is scanwidth 140, and T_(s) is traverse scan speed. The target fluence may bedecreased by decreasing the laser-beam average power, increasing scanwidth 140, and/or increasing the traverse scan speed. If scan width 140is decreased, the target fluence may be maintained by a compensatingincrease (inverse proportional) in the traverse scan speed.

Raster scan speed, scan width 140, and traverse scan speed areimplemented by scanning head 104 and laser-positioning apparatus 106.Scanning head 104 is configured to deliver laser beam 120 to surface 128in area 130 (i.e., in scan regions 136). Scanning head 104 is configuredto scan laser beam 120 a distance of scan width 140, for each of scanregions 136, in scan width direction 144 along scan line 132 at a rateof the raster scan speed. Scan line 132 is not necessarily a straightline and may be an arc, a curve, and/or a segmented line. Generally, theraster scan speed is much faster than the traverse scan speed such thatlaser beam 120, as it is scanned at raster scan speed, may be treated asa laser sheet. For example, the raster scan speed may be greater than1,000 times the traverse scan speed. Scanning head 104 is configured tooptically scan laser beam 120 because optically scanning laser beam 120is generally much faster than mechanically scanning laser beam 120.Scanning head 104 includes a laser scanning apparatus for high speedscanning such as a mirror galvanometer and/or a polygonal mirror.

Laser-positioning apparatus 106 is configured to scan laser beam 120 intraverse direction 146 across surface 128 by adjusting the relativeposition of surface 128 and scanning head 104 (which delivers laser beam120 to surface 128). Laser-positioning apparatus 106 adjusts therelative position according to the desired traverse scan speed for eachof scan regions 136. Laser-positioning apparatus 106 may move scanninghead 104 and/or workpiece 124 to achieve the relative motion of laserbeam 120 with respect to surface 128. Laser-positioning apparatus 106may include a gantry, stage, rail, positioner, etc. to move scanninghead 104 and/or workpiece 124. Laser-positioning apparatus 106 may beconfigured to support and/or move other components of laser ablationsystem 100 (e.g., laser 102 and/or controller 110).

Motion in scan width direction 144 (due to scanning head 104) may beindependent of motion in traverse direction 146 (due tolaser-positioning apparatus 106). For example, raster scan speed andtraverse scan speed may be varied independently. As another example,raster scan speed and traverse scan speed may be independent of thelocation of laser beam 120 relative to surface 128.

The following subject matter of this paragraph characterizes example 2of the present disclosure, wherein example 2 also includes the subjectmatter according to example 1, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 1, laser-positioning apparatus 106comprises at least one of a gantry or a robotic positioner.

Laser-positioning apparatus 106 is configured for automatic operationand may be configured for versatile positioning. A gantry permitsrelatively arbitrary positioning of scanning head 104 relative to anopen support space. A gantry permits positioning over a large distanceand may accommodate large and/or complex workpiece geometries. Forexample, workpiece 124 may be an aircraft wing or a mold to form afuselage section. A robotic positioner (also referred to as a roboticarm) permits relatively arbitrary positioning of scanning head 104relative to an open support space. A robotic positioner permitspositioning over a large volume and may accommodate large and/or complexworkpiece geometries.

The following subject matter of this paragraph characterizes example 3of the present disclosure, wherein example 3 also includes the subjectmatter according to any one of examples 1 to 2, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, scanning head104 comprises at least one of a polygonal mirror or a mirrorgalvanometer.

Scanning head 104 is configured to scan laser beam 120 in scan widthdirection 144 at the raster scan speed. The raster scan speed generallyis much faster than the traverse scan speed. A polygonal mirror and/or amirror galvanometer may optically deflect laser beam 120 to scan laserbeam 120 at a rapid raster scan speed. A polygonal mirror may be used toproduce a consistent raster scan speed over relatively constant scanwidth 140. A mirror galvanometer may be used to independently addressdifferent locations along scan line 132 and to select different scanwidths 140 for each of scan regions 136.

The following subject matter of this paragraph characterizes example 4of the present disclosure, wherein example 4 also includes the subjectmatter according to any one of examples 1 to 3, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, laser 102 isoptically coupled to scanning head 104 via at least one of a fiber opticor a free-space optical path.

Laser 102 is configured to provide laser beam 120 to scanning head 104.A fiber optic or a free-space optical path may permit motion of scanninghead 104 relative to laser 102. Additionally or alternatively, a fiberoptic or a free-space optical path may permit laser 102 to be locatedremote from scanning head 104, laser-positioning apparatus 106, and/orworkpiece 124. Laser 102 and/or workpiece 124 may be large objects.Laser 102 generally is a high powered laser and may use specializedelectrical connections and/or cooling apparatuses. Remote location mayfacilitate access to workpiece 124, laser-positioning apparatus 106,scanning head 104, and/or laser 102. Remote location may facilitateutility access to laser 102 (e.g., cooling water and/or electricalconnection).

The following subject matter of this paragraph characterizes example 5of the present disclosure, wherein example 5 also includes the subjectmatter according to any one of examples 1 to 4, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, laser 102 ismechanically coupled to laser-positioning apparatus 106.

Laser 102 may be mechanically coupled and/or supported tolaser-positioning apparatus 106. Being coupled and/or supported mayfacilitate a compact design of laser ablation system 100. Additionallyor alternatively, being coupled and/or supported may facilitate opticalrouting of laser beam 120 from laser 102 to scanning head 104 that maybe positioned by laser-positioning apparatus 106.

The following subject matter of this paragraph characterizes example 6of the present disclosure, wherein example 6 also includes the subjectmatter according to any one of examples 1 to 5, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, laser 102 isat least one of a pulsed laser, a mode-locked laser, and a Q-switchedlaser.

Laser beam 120 has temporal structure that may be in the form of pulses.A pulsed laser, a mode-locked laser, and a Q-switched laserintrinsically emit a pulsed laser beam. Pulsed laser beams may have amuch higher peak power than average power. For example, the peak powerof a pulsed laser beam is inversely related to the duty cycle of thelaser beam (the laser pulse width relative to the laser repetitionperiod). A pulsed laser beam may have a duty cycle of less than 0.001and, hence, may have a peak power greater than 1,000 times thelaser-beam average power. High peak powers may lead to high targetirradiances and, hence, high cleaning effectiveness and/or short laserablation times.

The following subject matter of this paragraph characterizes example 7of the present disclosure, wherein example 7 also includes the subjectmatter according to any one of examples 1 to 6, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, the targetfluence is, for each one of scan regions 136, the laser-beam averagepower divided by a product of the scan width and the traverse scanspeed. The target irradiance is, for each one of scan regions 136, thelaser-beam average power divided by a product of the laser pulserepetition rate, the laser pulse width, and the laser-beam spot area.

The cleaning effectiveness of laser ablation system 100 is determined bythe target fluence and the target irradiance. For each of scan regions136, the same target fluence and target irradiance may be used toprovide the same cleaning effectiveness for each of scan regions 136.

The following subject matter of this paragraph characterizes example 8of the present disclosure, wherein example 8 also includes the subjectmatter according to any one of examples 1 to 7, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, laser beam 120is configured to ablate area 130 of surface 128 when laser beam 120 isapplied along a nominal scan width with the target fluence and thetarget irradiance. The target fluence is a nominal laser-beam averagepower divided by a product of the nominal scan width and a nominaltraverse scan speed. The target irradiance is the nominal laser-beamaverage power divided by a product of a nominal laser pulse repetitionrate, a nominal laser pulse width, and a nominal laser-beam spot area.

Selection of a nominal scan width, a target fluence, and a targetirradiance may provide sufficient information to determine a nominallaser-beam average power, a nominal traverse scan speed, a nominal laserpulse repetition rate, a nominal laser pulse width, and/or a nominallaser-beam spot area. Alternatively, the nominal parameters may definethe target fluence and target irradiance. Selection of nominal scanwidth, target fluence, and/or target irradiance may be useful to tunelaser ablation system 100 to ablate different materials (the material tobe removed) and/or to preserve different materials (of surface 128) asmay be present on various workpieces 124.

The following subject matter of this paragraph characterizes example 9of the present disclosure, wherein example 9 also includes the subjectmatter according to any one of examples 1 to 8, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, controller 110is configured to receive scan regions 136 of area 130 of surface 128.

Scan regions 136 may be determined by inspection or modelling of surface128. Scan regions 136 may be determined by sectioning area 130 into aseries of regions, each of which may be described by only one scan width140 for the region (individual ones of scan regions 136). Scan regions136 may be determined by other devices and/or a human operator and thenprovided to controller 110 to follow the pattern of scan regions 136provided. Hence, controller 110 may be dedicated to scanning operationsand may not need to determine scan regions 136.

The following subject matter of this paragraph characterizes example 10of the present disclosure, wherein example 10 also includes the subjectmatter according to any one of examples 1 to 9, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, controller 110is programmed to determine scan regions 136 of area 130 of surface 128based upon a virtual model of surface 128.

Scan regions 136 may be determined by identifying area 130 of surface128 and sectioning area 130 into scan regions 136. A virtual model ofsurface 128 and/or workpiece 124 may facilitate precise determination oflocation of area 130 and/or scan regions 136. The virtual model may be atwo-dimensional (2D) or three-dimensional (3D) model and may be anelectronic description of surfaces, boundaries, and/or points thatdescribe surface 128 and/or workpiece 124. For example, the virtualmodel may be a CAD (computer aided design) model, a boundaryrepresentation, and/or a surface tessellation.

The following subject matter of this paragraph characterizes example 11of the present disclosure, wherein example 11 also includes the subjectmatter according to example 10, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 1, controller 110 is programmed todetermine scan width 140 of each one of scan regions 136 based upon thevirtual model of surface 128.

Each one of scan regions 136 may have different scan width 140 (at leastone scan width 140 is different). Scan width 140 of each one of scanregions 136 may be determined by the size of scan regions 136 and/orarea 130 determined from the virtual model of surface 128. The virtualmodel of surface 128 and/or workpiece 124 may facilitate precisedetermination of scan width 140 for each one of scan regions 136.

The following subject matter of this paragraph characterizes example 12of the present disclosure, wherein example 12 also includes the subjectmatter according to any one of examples 10 to 11, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 2, the virtualmodel of surface 128 is a three-dimensional (3D) model.

The 3D model may facilitate determining positions and/or orientations ofscanning head 104 relative to surface 128. For example, the 3D model maybe used to establish and/or maintain scan spacing 148 between scanninghead 104 and surface 128.

The following subject matter of this paragraph characterizes example 13of the present disclosure, wherein example 13 also includes the subjectmatter according to any one of examples 10 to 12, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, the virtualmodel of surface 128 is based upon an image of surface 128.

The image of surface 128 may provide information on the shape and/orstructure of surface 128 as actually present on surface 128. Virtualmodels based on design data may not reflect the present shape and/orstructure of surface 128 after manufacture or use.

The following subject matter of this paragraph characterizes example 14of the present disclosure, wherein example 14 also includes the subjectmatter according to example 13, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 1, laser ablation system 100 furthercomprises machine vision system 112, configured to image surface 128.The image of surface 128 is acquired by machine vision system 112.

Machine vision system 112 may automatically collect images of surface128 and/or provide images of surface 128 as it is situated with respectto laser ablation system 100. Machine vision system 112 may be used toacquire images for alignment of workpiece 124 and/or surface 128.Machine vision system 112 may be controlled by controller 110.Integrating machine vision system 112 within laser ablation system 100may facilitate alignment of surface 128 and/or acquisition of the imageto create the virtual model of surface 128.

The following subject matter of this paragraph characterizes example 15of the present disclosure, wherein example 15 also includes the subjectmatter according to any one of examples 1 to 14, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, controller 110is programmed to identify a first one of scan regions 136 on surface 128to be scanned by laser beam 120.

Laser ablation of surface 128 begins at one of scan regions 136 andcontinues with each of the other scan regions 136. The first one of scanregions 136 may be selected based upon proximity to an edge of area 130and/or proximity to other scan regions 136. Ordering of scan regions 136permits efficient laser ablation of area 130 of surface 128. Forexample, arranging first one of scan regions 136 and subsequent scanregions 136 such that completion of the first one of scan regions 136(and subsequent scan regions 136) is at or near the next one of scanregions 136 permits laser ablation system 100 to scan area 130 withlittle time (or no time) devoted to moving between scan regions 136

The following subject matter of this paragraph characterizes example 16of the present disclosure, wherein example 16 also includes the subjectmatter according to example 15, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 1, laser ablation system 100 furthercomprises machine vision system 112. Controller 110 is furtherprogrammed to cause machine vision system 112 to acquire an image ofsurface 128 and to identify a location and an orientation of surface 128in a coordinate system of laser ablation system 100 based at least inpart upon the image of surface 128, acquired by machine vision system112.

Machine vision system 112 may automatically collect images of surface128 and/or provide images of surface 128 as it is situated with respectto laser ablation system 100. Machine vision system 112 may be used toacquire images for alignment of workpiece 124 and/or surface 128.Machine vision system 112 may be positioned in a known location and/ororientation with respect to other components of laser ablation system100. Additionally or alternatively, machine vision system 112 may beconfigured to image surface 128 with reference fiducials or othermarkers in the image frame. The known location, known orientation,reference fiducials, and/or other markers provide a reference toestablish and/or relate to the coordinate system of laser ablationsystem 100. Integrating machine vision system 112 within laser ablationsystem 100 may facilitate alignment of surface 128.

The following subject matter of this paragraph characterizes example 17of the present disclosure, wherein example 17 also includes the subjectmatter according to any one of examples 15 to 16, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, controller 110is further programmed to identify the first one of scan regions 136 onsurface 128 to be scanned by laser beam 120 based upon a virtual modelof surface 128.

The first one of scan regions 136 may be determined by identifying area130 of surface 128 and selecting the first one of scan regions 136 basedupon proximity to an edge of area 130 and/or proximity to other scanregions 136. A virtual model of surface 128 and/or workpiece 124 mayfacilitate precise determination of location of area 130 and/or scanregions 136 (including the first one of scan regions 136).

The following subject matter of this paragraph characterizes example 18of the present disclosure, wherein example 18 also includes the subjectmatter according to example 17, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 2, the virtual model of surface 128 is athree-dimensional (3D) model.

The 3D model may facilitate determining positions and/or orientations ofscanning head 104 relative to surface 128. For example, the 3D model maybe used to establish and/or maintain scan spacing 148 between scanninghead 104 and surface 128.

The following subject matter of this paragraph characterizes example 19of the present disclosure, wherein example 19 also includes the subjectmatter according to any one of examples 1 to 18, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, controller 110is programmed to determine the traverse scan speed, the laser-beamaverage power, the laser pulse repetition rate, the laser pulse width,and the laser-beam spot area by equating the traverse scan speed to amaximum traverse scan speed and determining the laser pulse repetitionrate in proportion to scan width 140 for each one of scan regions 136when scan width 140 is less than a first critical scan width and greaterthan or equal to a second critical scan width. The first critical scanwidth is greater than the second critical scan width.

Laser ablation system 100 may have a maximum traverse scan speed. Forexample, traverse scan speed may be limited by reliable operation ofmechanical components (i.e., components of laser-positioning apparatus106) translating scanning head 104 and/or workpiece 124. For scanregions 136 in which scan width 140 is less than the first critical scanwidth (e.g., S₁ in FIG. 3), target fluence may be achieved by selectinga traverse scan speed greater than the maximum traverse scan speed.Smaller scan width 140 requires larger traverse scan speed to producethe same target fluence. If scan width 140 is small enough (i.e., lessthan the first critical scan width) to imply a traverse scan speedgreater than the maximum traverse scan speed, traverse scan speed may beset to the maximum traverse scan speed and the laser-beam average powerreduced to achieve the target fluence based on the maximum traverse scanspeed and scan width 140 that is less than the first critical scanwidth. The laser-beam average power may be reduced in proportion to scanwidth 140 (according to Eq. 2) to achieve the target fluence. Laser-beamaverage power may be reduced in proportion to laser pulse repetitionrate while maintaining the target irradiance (according to Eq. 1).Hence, to achieve both the target fluence and the target irradiance, thelaser pulse repetition rate may be reduced in proportion to scan width140 while the traverse scan speed is at the maximum traverse scan speed.Laser ablation system 100 may have a second critical scan width (e.g.,S₂ in FIG. 3) below which this algorithm is not practical, desired, orreliable.

The following subject matter of this paragraph characterizes example 20of the present disclosure, wherein example 20 also includes the subjectmatter according to any one of examples 1 to 19, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, controller 110is programmed to determine the traverse scan speed, the laser-beamaverage power, the laser pulse repetition rate, the laser pulse width,and the laser-beam spot area by equating the traverse scan speed to amaximum traverse scan speed, equating the laser pulse repetition rate toa minimum laser pulse repetition rate, and determining the laser pulsewidth in proportion to scan width 140 for each one of scan regions 136when scan width 140 is less than a second critical scan width andgreater than or equal to a third critical scan width. The secondcritical scan width is greater than the third critical scan width.

Laser ablation system 100 may have a maximum traverse scan speed and aminimum laser pulse repetition rate. The maximum traverse scan speed maybe as described with respect to example 19. The minimum laser pulserepetition rate may be due to limits of laser 102 operation. For scanregions 136 in which scan width 140 is less than the second criticalscan width (e.g., S₂ in FIG. 3), target fluence may be achieved byselecting a traverse scan speed greater than the maximum traverse scanspeed and/or by selecting a traverse scan speed at the maximum traversescan speed and selecting a laser pulse repetition rate less than theminimum laser pulse repetition rate. Smaller scan width 140 requireslarger traverse scan speed to produce the same target fluence andsmaller laser pulse repetition to achieve the same target fluence andtarget irradiance. If scan width 140 is small enough (i.e., less thanthe second critical scan width) to imply a traverse scan speed at themaximum traverse scan speed and a laser pulse repetition rate less thanthe minimum laser pulse repetition rate, traverse scan speed may be setto the maximum traverse scan speed, laser pulse repetition rate may beset to the minimum laser pulse repetition rate, and the laser-beamaverage power reduced to achieve the target fluence based on the maximumtraverse scan speed and scan width 140 that is less than the secondcritical scan width. The laser-beam average power may be reduced inproportion to scan width 140 (according to Eq. 2) to achieve the targetfluence. Laser-beam average power may be reduced in proportion to laserpulse width while maintaining the target irradiance (according to Eq.1). Hence, to achieve both the target fluence and the target irradiance,the laser pulse width may be reduced in proportion to scan width 140while the traverse scan speed is at the maximum traverse scan speed andthe laser pulse repetition rate is at the minimum laser pulse repetitionrate. Laser ablation system 100 may have a third critical scan width(e.g., S₃ in FIG. 3) below which this algorithm is not practical,desired, or reliable.

The following subject matter of this paragraph characterizes example 21of the present disclosure, wherein example 21 also includes the subjectmatter according to any one of examples 1 to 20, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, controller 110is programmed to determine the traverse scan speed, the laser-beamaverage power, the laser pulse repetition rate, the laser pulse width,and the laser-beam spot area by equating the traverse scan speed to amaximum traverse scan speed, equating the laser pulse repetition rate toa minimum laser pulse repetition rate, equating the laser pulse width toa minimum laser pulse width, and determining the laser-beam spot area inproportion to scan width 140 for each one of scan regions 136 when scanwidth 140 is less than a third critical scan width.

Laser ablation system 100 may have a maximum traverse scan speed, aminimum laser pulse repetition rate, and a minimum laser pulse width.The maximum traverse scan speed and minimum laser pulse repetition ratemay be as described with respect to examples 19 and 20. The minimumlaser pulse width may be due to limits of laser 102 operation. For scanregions 136 in which scan width 140 is less than the third critical scanwidth (e.g., S₃ in FIG. 3), target fluence may be achieved by selectinga traverse scan speed greater than the maximum traverse scan speed, byselecting a traverse scan speed at the maximum traverse scan speed andselecting a laser pulse repetition rate less than the minimum laserpulse repetition rate, and/or by selecting a traverse scan speed at themaximum traverse scan speed, selecting a laser pulse repetition rate atthe minimum laser pulse repetition rate, and selecting a laser pulsewidth less than the minimum laser pulse width. Smaller scan width 140requires larger traverse scan speed to produce the same target fluence,smaller laser pulse repetition to achieve the same target fluence andtarget irradiance, and smaller laser pulse width to achieve the sametarget fluence and target irradiance. If scan width 140 is small enough(i.e., less than the third critical scan width) to imply a traverse scanspeed at the maximum traverse scan speed, a laser pulse repetition rateat the minimum laser pulse repetition rate, and a laser pulse width lessthan the minimum laser pulse width, traverse scan speed may be set tothe maximum traverse scan speed, laser pulse repetition rate may be setto the minimum laser pulse repetition rate, laser pulse width may be setto the minimum laser pulse width, and the laser-beam average powerreduced to achieve the target fluence based on the maximum traverse scanspeed and scan width 140 that is less than the third critical scanwidth. The laser-beam average power may be reduced in proportion to scanwidth 140 (according to Eq. 2) to achieve the target fluence. Laser-beamaverage power may be reduced in proportion to laser-beam spot area whilemaintaining the target irradiance (according to Eq. 1). Hence, toachieve both the target fluence and the target irradiance, thelaser-beam spot area may be reduced in proportion to scan width 140while the traverse scan speed is at the maximum traverse scan speed, thelaser pulse repetition rate is at the minimum laser pulse repetitionrate, and the laser pulse width is at the minimum laser pulse width.Laser ablation system 100 may have a fourth critical scan width (e.g.,S₄ in FIG. 3) below which this algorithm is not practical, desired, orreliable.

The following subject matter of this paragraph characterizes example 22of the present disclosure, wherein example 22 also includes the subjectmatter according to any one of examples 1 to 21, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, scan regions136 are contiguous so that area 130 is continuous.

Scan regions 136 are contiguous with each other, i.e., neighboring scanregions 136 touch, partially overlap, and/or connect with each other.With contiguous scan regions 136, laser beam 120 may be scanned from oneof scan regions 136 to the next of scan regions 136 in a continuousmotion, without needing to translate surface 128 relative to scanninghead 104 between scan regions 136. Hence, scanning contiguous scanregions 136 does not need to incur delay between scan regions 136 andconsequent inefficiency of ablation of area 130. Contiguous scan regions136 provide for area 130 that is continuous and that may becharacterized by having a single boundary to encompass all of scanregions 136. Area 130 that is continuous may have no internal voids orvacancies (regions not included in one of scan regions 136).

The following subject matter of this paragraph characterizes example 23of the present disclosure, wherein example 23 also includes the subjectmatter according to any one of examples 1 to 22, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, area 130 ofsurface 128 comprises scan regions 136.

Area 130 may comprise scan regions 136, may consist essentially of scanregions 136, and may comprise only scan regions 136. Scan regions 136may be derived by sectioning area 130 such that each of scan regions 136is a portion of area 130.

The following subject matter of this paragraph characterizes example 24of the present disclosure, wherein example 24 also includes the subjectmatter according to any one of examples 1 to 23, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 2, controller 110is programmed to cause scanning head 104 to move laser beam 120 acrossarea 130 of surface 128 with scan spacing 148 separating scanning head104 from area 130 of surface 128.

Scan spacing 148 between scanning head 104 and area 130 of surface 128may provide clearance and/or avoid contact between scanning head 104 andsurface 128. Scan spacing 148 may be at focal point of laser beam 120(if laser beam 120 has a focal point outside of scanning head 104)and/or may function to establish the laser-beam spot area as laser beam120 is scanned across area 130.

The following subject matter of this paragraph characterizes example 25of the present disclosure, wherein example 25 also includes the subjectmatter according to example 24, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 2, scan spacing 148, separating scanninghead 104 from area 130 of surface 128, is substantially constant withineach one of scan regions 136.

Substantially constant (or uniform) scan spacing 148 within one of scanregions 136 may establish a substantially constant (or uniform)laser-beam spot area in that one of scan regions 136. For each of scanregions 136, scan spacing 148 may be substantially constant (oruniform), though different ones of scan regions 136 may be scanned withdifferent scan spacing 148 values. Scan spacing 148 (and hence possiblythe laser-beam spot area) may be optimized for each one of scan regions136 independently.

The following subject matter of this paragraph characterizes example 26of the present disclosure, wherein example 26 also includes the subjectmatter according to any one of examples 24 to 25, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 2, scan spacing148, separating scanning head 104 from area 130 of surface 128, issubstantially constant for all scan regions 136.

Scan spacing 148 may not vary between scan regions 136, which mayfacilitate transitions between scan regions 136 without translation ofsurface 128 relative to scanning head 104. Substantially constant (oruniform) scan spacing 148 for all scan regions 136 may not precludeadjustment of laser-beam spot area. The laser-beam spot area may bevaried as necessary or desired by adjusting the focal distance of laserbeam 120 from scanning head 104.

The following subject matter of this paragraph characterizes example 27of the present disclosure, wherein example 27 also includes the subjectmatter according to any one of examples 1 to 26, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 1, controller 110is programmed to cause scanning head 104 to move laser beam 120 acrossarea 130 of surface 128 with an angle of incidence substantially normalto each one of scan regions 136.

Scanning each of scan regions 136 at a perpendicular (normal) angle ofincidence may provide for effective ablation in scan regions 136. Laserbeam 120 may have higher (or maximum) target irradiance when laser beam120 is oriented normal to surface 128. If laser beam 120 impingessurface 128 at an angle significantly different from normal(perpendicular), the spot of laser beam 120 may distort and becomelarger (thus reducing target irradiance). As used herein, a normal angleof incidence is approximately perpendicular to surface 128 (at about90°, e.g., within the range of 80°-90°).

Referring generally to FIGS. 1-3 and particularly to, e.g., FIG. 4,method 200 of using laser ablation system 100 to clean area 130 ofsurface 128 with laser beam 120 is disclosed. Laser beam 120 has atarget fluence and a target irradiance. Area 130 comprises scan regions136, each having scan width 140. Method 200 comprises (block 202)determining traverse scan speed, laser-beam average power, laser pulserepetition rate, laser pulse width, and laser-beam spot area of laserbeam 120 for each one of scan regions 136 to achieve the target fluenceand the target irradiance of laser beam 120 when scanning each one ofscan regions 136 with laser beam 120. Scan width 140 of at least one ofscan regions 136 is different from scan width 140 of another one of scanregions 136. Method 200 also comprises (block 204) scanning, across scanwidth 140, each one of scan regions 136 of area 130 with laser beam 120at the target fluence and the target irradiance. The preceding subjectmatter of this paragraph characterizes example 28 of the presentdisclosure.

Method 200 applies a uniform target fluence and a uniform targetirradiance to all of scan regions 136 so that area 130 is uniformlyablated. Cleaning effectiveness is determined by target fluence andtarget irradiance. By selecting the target fluence and the targetirradiance appropriately, area 130 may be efficiently ablated withoutsignificant over ablation, significant under ablation, or scanning ofregions outside of area 130. Relative to conventional laser ablation,changes in scan width 140 between scan regions 136 are compensated tomaintain the target fluence and the target irradiance for all of scanregions 136.

Operation parameters (e.g., traverse scan speed, laser-beam averagepower, laser pulse repetition rate, laser pulse width, and laser-beamspot area) are determined independently for each one of scan regions 136based on scan width 140 for that one of scan regions 136, the targetfluence, and the target irradiance. Operation parameters may bedetermined based on target fluence and target irradiance as described inEq. 1 and 2. At least one of the operation parameters is changed for atleast one of scan regions 136 because at least one scan width 140 isdifferent among scan regions 136.

Scan regions 136 are arranged within area 130 of surface 128 and areordered. Sequentially scanning (block 204) comprises scanning each oneof scan regions 136, one after the other, in sequential order. Scanningsequentially may reduce time moving scanning head 104, laser beam 120,and/or workpiece 124 between scan regions 136 and, hence, may increaseefficiency relative to scanning out of order.

The following subject matter of this paragraph characterizes example 29of the present disclosure, wherein example 29 also includes the subjectmatter according to example 28, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, when scanwidth 140 of at least one of scan regions 136 is different from scanwidth 140 of another one of scan regions 136, at least one of thetraverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, or the laser-beam spot area oflaser beam 120 for at least the one of scan regions 136 is differentfrom at least one of the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, or thelaser-beam spot area of laser beam 120 for the other one of scan regions136.

To maintain the target fluence and the target irradiance for all of scanregions 136, one or more changes in the traverse scan speed, thelaser-beam average power, the laser pulse repetition rate, the laserpulse width and/or the laser-beam spot area may be used to compensatefor changes in scan width 140 among scan regions 136. Compensatingchanges may be determined using Eq. 1 and 2.

The following subject matter of this paragraph characterizes example 30of the present disclosure, wherein example 30 also includes the subjectmatter according to any one of examples 28 to 29, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, laser beam 120 has an initial laser-beam average power. Forat least one of scan regions 136, the traverse scan speed is the initiallaser-beam average power divided by a product of scan width 140 of atleast the one of scan regions 136 and the target fluence.

The traverse scan speed may be determined using Eq. 2, i.e., thetraverse scan speed is the laser-beam average power divided by a productof scan width 140 and target fluence. If initial laser-beam averagepower and scan width 140 (for at least one of scan regions 136) issuitable to set traverse scan speed (e.g., the calculated traverse scanspeed is within limits of operation), the traverse scan speed is theproduct of scan width 140 of at least one of scan regions 136 and thetarget fluence. Setting traverse scan speed according to Eq. 2 permitscompensation of changes in scan width 140 without affecting laser outputparameters.

The following subject matter of this paragraph characterizes example 31of the present disclosure, wherein example 31 also includes the subjectmatter according to any one of examples 28 to 30, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, laser beam 120 has an initial laser-beam average power. Scanregions 136 comprise an adapted scan region. Determining the traversescan speed, the laser-beam average power, the laser pulse repetitionrate, the laser pulse width, and the laser-beam spot area for each oneof scan regions 136 comprises determining that a projected traverse scanspeed for the adapted scan region is greater than a maximum traversescan speed. The projected traverse scan speed for the adapted scanregion is the initial laser-beam average power divided by a product ofscan width 140 of the adapted scan region and the target fluence. Method200 further comprises determining an adapted laser-beam average powerthat is a product of the target fluence, scan width 140 of the adaptedscan region, and the maximum traverse scan speed.

Laser ablation system 100 may have a maximum traverse scan speed. Forexample, traverse scan speed may be limited by reliable operation ofmechanical components (i.e., components of laser-positioning apparatus106) translating scanning head 104 and/or workpiece 124. For scanregions 136 in which scan width 140 is less than a first critical scanwidth (e.g., S₁ in FIG. 3), target fluence may be achieved by selectinga projected traverse scan speed greater than the maximum traverse scanspeed. Such scan regions 136 may be referred to as adapted scan regionsbecause adaptation of operation parameters is required to achieve thetarget fluence and not exceed the maximum traverse scan speed. Foradapted scan regions, the projected traverse scan speed may be set tothe maximum traverse scan speed and the adapted laser-beam average powermay be reduced from the initial laser-beam average power to achieve thetarget fluence based on the maximum traverse scan speed and scan width140 of the adapted scan region. The adapted laser-beam average power maybe set according to Eq. 2, i.e., the adapted laser-beam average power isthe product of the target fluence, scan width 140 of the adapted scanregion, and the maximum traverse scan speed.

The following subject matter of this paragraph characterizes example 32of the present disclosure, wherein example 32 also includes the subjectmatter according to example 31, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, the laserpulse repetition rate of the adapted scan region is the adaptedlaser-beam average power divided by a product of the target irradiance,the laser pulse width for the adapted scan region, and the laser-beamspot area for the adapted scan region. Scanning area 130 of surface 128comprises scanning the adapted scan region at the maximum traverse scanspeed across scan width 140 of the adapted scan region while laser beam120 has the adapted laser-beam average power, the laser pulse repetitionrate for the adapted scan region, the laser pulse width for the adaptedscan region, and the laser-beam spot area for the adapted scan region.

Further adaptation of operation parameters (beyond that described inexample 31) may be achieved by adjusting the laser pulse repetition rateof the adapted scan region according to Eq. 1. Specifically, the laserpulse repetition rate of the adapted scan region is the adaptedlaser-beam average power divided by a product of the target irradiance,the laser pulse width for the adapted scan region, and the laser-beamspot area for the adapted scan region. Further adapting in this mannerpermits maintaining the target irradiance while adapting the laser-beamaverage power to maintain the target fluence.

The following subject matter of this paragraph characterizes example 33of the present disclosure, wherein example 33 also includes the subjectmatter according to example 31, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, determiningthe traverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, and the laser-beam spot area foreach one of scan regions 136 comprises determining that a projectedlaser pulse repetition rate for the adapted scan region is less than aminimum laser pulse repetition rate. The projected laser pulserepetition rate for the adapted scan region is the adapted laser-beamaverage power divided by a product of the target irradiance, the laserpulse width for the adapted scan region, and the laser-beam spot areafor the adapted scan region.

Laser ablation system 100 may have a minimum laser pulse repetitionrate. The minimum laser pulse repetition rate may be due to limits oflaser 102 operation. For scan regions 136 in which scan width 140 isless than a second critical scan width (e.g., S₂ in FIG. 3), targetfluence and target irradiance may be achieved by selecting a projectedtraverse scan speed at the maximum traverse scan speed and by selectinga projected laser pulse repetition rate less than the minimum laserpulse repetition rate. For these adapted scan regions, the projectedtraverse scan speed may be set to the maximum traverse scan speed, theprojected laser pulse repetition rate at the minimum laser pulserepetition rate, and the adapted laser-beam average power may be reducedfrom the initial laser-beam average power to achieve the target fluenceand the target irradiance based on the maximum traverse scan speed, theminimum laser pulse repetition rate, and scan width 140 of the adaptedscan region. The adapted laser-beam average power may be set accordingto the minimum laser pulse repetition rate and Eq. 1.

The following subject matter of this paragraph characterizes example 34of the present disclosure, wherein example 34 also includes the subjectmatter according to example 33, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, the laserpulse width for the adapted scan region is the adapted laser-beamaverage power divided by a product of the target irradiance, the minimumlaser pulse repetition rate, and the laser-beam spot area for theadapted scan region. Scanning area 130 of surface 128 comprises scanningthe adapted scan region at the maximum traverse scan speed across scanwidth 140 of the adapted scan region while laser beam 120 has theadapted laser-beam average power, the minimum laser pulse repetitionrate, the laser pulse width for the adapted scan region, and thelaser-beam spot area for the adapted scan region.

Further adaptation of operation parameters (beyond that described inexample 33) may be achieved by adjusting the laser pulse width of theadapted scan region according to Eq. 1. Specifically, the laser pulsewidth of the adapted scan region is the adapted laser-beam average powerdivided by a product of the target irradiance, the minimum laser pulserepetition rate, and the laser-beam spot area for the adapted scanregion. Further adapting in this manner permits maintaining the targetirradiance while adapting the laser-beam average power to maintain thetarget fluence.

The following subject matter of this paragraph characterizes example 35of the present disclosure, wherein example 35 also includes the subjectmatter according to example 33, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, determiningthe traverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, and the laser-beam spot area foreach one of scan regions 136 comprises determining that a projectedlaser pulse width for the adapted scan region is less than a minimumlaser pulse width. The projected laser pulse width for the adapted scanregion is the adapted laser-beam average power divided by a product ofthe target irradiance, the minimum laser pulse repetition rate, and thelaser-beam spot area for the adapted scan region. The laser-beam spotarea for the adapted scan region is the adapted laser-beam average powerdivided by a product of the target irradiance, the minimum laser pulserepetition rate, and the minimum laser pulse width. Scanning area 130 ofsurface 128 comprises scanning the adapted scan region at the maximumtraverse scan speed across scan width 140 of the adapted scan regionwhile laser beam 120 has the adapted laser-beam average power, theminimum laser pulse repetition rate, the minimum laser pulse width, andthe laser-beam spot area for the adapted scan region.

Laser ablation system 100 may have a minimum laser pulse width. Theminimum laser pulse width may be due to limits of laser 102 operation.For scan regions 136 in which scan width 140 is less than a thirdcritical scan width (e.g., S₃ in FIG. 3), target fluence and targetirradiance may be achieved by selecting a projected traverse scan speedat the maximum traverse scan speed, by selecting a projected laser pulserepetition rate at the minimum laser pulse repetition rate, and byselecting a projected laser pulse width less than the minimum laserpulse width. For these adapted scan regions, the projected traverse scanspeed may be set to the maximum traverse scan speed, the projected laserpulse repetition rate at the minimum laser pulse repetition rate, theprojected laser pulse width at the minimum laser pulse width, and theadapted laser-beam average power may be reduced from the initiallaser-beam average power to achieve the target fluence and the targetirradiance based on the maximum traverse scan speed, the minimum laserpulse repetition rate, the minimum laser pulse width, and scan width 140of the adapted scan region. The adapted laser-beam average power may beset according to the minimum laser pulse repetition rate, minimum laserpulse width, and Eq. 1.

The following subject matter of this paragraph characterizes example 36of the present disclosure, wherein example 36 also includes the subjectmatter according to any one of examples 28 to 35, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises receiving information descriptive of scan regions 136of area 130 of surface 128.

Scan regions 136 may be determined by inspection or modelling of surface128. Scan regions 136 may be determined by sectioning area 130 into aseries of regions, each of which may be described by only one scan width140 for the region (individual ones of scan regions 136). Scan regions136 may be determined by other devices and/or a human operator and thenreceived in method 200. The information descriptive of scan regions 136may include the locations, orientations, boundaries, and/or order ofscan regions 136. The information received may be used to scan laserbeam 120 in scan regions 136 as described.

The following subject matter of this paragraph characterizes example 37of the present disclosure, wherein example 37 also includes the subjectmatter according to any one of examples 28 to 36, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises defining scan regions 136 of area 130 of surface 128based upon a virtual model of surface 128.

Scan regions 136 may be defined by identifying area 130 of surface 128and sectioning area 130 into scan regions 136. A virtual model ofsurface 128 and/or workpiece 124 may facilitate precise determination oflocation of area 130 and/or scan regions 136. The virtual model may be a2D or 3D model and may be an electronic description of surfaces,boundaries, and/or points that describe surface 128 and/or workpiece124. For example, the virtual model may be a CAD model, a boundaryrepresentation, and/or a surface tessellation.

The following subject matter of this paragraph characterizes example 38of the present disclosure, wherein example 38 also includes the subjectmatter according to example 37, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, method 200 further comprisesdetermining scan width 140 of each one of scan regions 136 based uponthe virtual model of surface 128.

Each one of scan regions 136 may have different scan width 140 (at leastone scan width 140 is different). Scan width 140 of each one of scanregions 136 may be determined by the size of scan regions 136 and/orarea 130 determined from the virtual model of surface 128. The virtualmodel of surface 128 and/or workpiece 124 may facilitate precisedetermination of scan width 140 for each one of scan regions 136.

The following subject matter of this paragraph characterizes example 39of the present disclosure, wherein example 39 also includes the subjectmatter according to any one of examples 37 to 38, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, the virtual model of surface 128 is a three-dimensional (3D)model.

The 3D model may facilitate determining positions and/or orientations ofscanning head 104 relative to surface 128. For example, the 3D model maybe used to establish and/or maintain scan spacing 148 between scanninghead 104 and surface 128.

The following subject matter of this paragraph characterizes example 40of the present disclosure, wherein example 40 also includes the subjectmatter according to any one of examples 37 to 39, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, the virtual model of surface 128 is based upon an image ofsurface 128.

The image of surface 128 may provide information on the shape and/orstructure of surface 128 as actually present on surface 128. Virtualmodels based on design data may not reflect the present shape and/orstructure of surface 128 after manufacture or use.

The following subject matter of this paragraph characterizes example 41of the present disclosure, wherein example 41 also includes the subjectmatter according to any one of examples 28 to 40, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises identifying a first one of scan regions 136 on surface128 to be scanned by laser beam 120.

Sequentially scanning (block 204) of surface 128 begins at one of scanregions 136 and continues with each of the other scan regions 136. Thefirst one of scan regions 136 may be selected based upon proximity to anedge of area 130 and/or proximity to other scan regions 136. Ordering ofscan regions 136 permits efficient laser ablation of area 130 of surface128. For example, arranging first one of scan regions 136 and subsequentscan regions 136 such that completion of the first one of scan regions136 (and subsequent scan regions 136) is at or near the next one of scanregions 136 permits laser ablation system 100 to scan area 130 withlittle time (or no time) devoted to moving between scan regions 136

The following subject matter of this paragraph characterizes example 42of the present disclosure, wherein example 42 also includes the subjectmatter according to example 41, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, identifyingthe first one of scan regions 136 on surface 128 to be scanned by laserbeam 120 comprises locating and particularly orienting surface 128 in acoordinate system of scan regions 136.

Locating and particularly orienting surface 128 in the coordinate systemof scan regions 136 may include locating and orienting workpiece 124with mechanical or optical features to place the workpiece 124 asdesired. Locating and orienting workpiece 124 may facilitate identifyingthe first one of scan regions 136 (e.g., selecting the one of scanregions 136 nearest the origin of the coordinate system and/or nearestthe edge of surface 128).

The following subject matter of this paragraph characterizes example 43of the present disclosure, wherein example 43 also includes the subjectmatter according to example 41, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, identifyingthe first one of scan regions 136 on surface 128 to be scanned by laserbeam 120 comprises probing surface 128 to identify a location and anorientation of surface 128 in a coordinate system of laser ablationsystem 100.

Probing surface 128 to identify a location and an orientation of surface128 in a coordinate system of laser ablation system 100 may includecontacting surface 128 or using optical tools (e.g., laser range finder)to identify the location and orientation of workpiece 124 and/or surface128 as placed in laser ablation system 100.

The following subject matter of this paragraph characterizes example 44of the present disclosure, wherein example 44 also includes the subjectmatter according to example 41, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, identifyingthe first one of scan regions 136 on surface 128 to be scanned by laserbeam 120 comprises imaging surface 128 to identify a location and anorientation of surface 128 in a coordinate system of laser ablationsystem 100.

Imaging surface 128 may include imaging from a known location and/ororientation with respect to the coordinate system of laser ablationsystem 100. Additionally or alternatively, imaging surface 128 mayinclude acquiring images with reference fiducials or other markers inthe image frame. The known location, known orientation, referencefiducials, and/or other markers provide a reference to establish and/orrelate to the coordinate system of laser ablation system 100.

The following subject matter of this paragraph characterizes example 45of the present disclosure, wherein example 45 also includes the subjectmatter according to any one of examples 41 to 44, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, identifying the first one of scan regions 136 on surface 128to be scanned by laser beam 120 is based upon a virtual model of surface128.

The first one of scan regions 136 may be determined by identifying area130 of surface 128 and selecting the first one of scan regions 136 basedupon proximity to an edge of area 130 and/or proximity to other scanregions 136. A virtual model of surface 128 and/or workpiece 124 mayfacilitate precise determination of location of area 130 and/or scanregions 136 (including the first one of scan regions 136).

The following subject matter of this paragraph characterizes example 46of the present disclosure, wherein example 46 also includes the subjectmatter according to example 45, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, the virtualmodel of surface 128 is a three-dimensional (3D) model.

The 3D model may facilitate determining positions and/or orientations ofscanning head 104 relative to surface 128. For example, the 3D model maybe used to establish and/or maintain scan spacing 148 between scanninghead 104 and surface 128.

The following subject matter of this paragraph characterizes example 47of the present disclosure, wherein example 47 also includes the subjectmatter according to any one of examples 45 to 46, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, the virtual model of surface 128 is based upon an image ofsurface 128.

The image of surface 128 may provide information on the shape and/orstructure of surface 128 as actually present on surface 128. Virtualmodels based on design data may not reflect the present shape and/orstructure of surface 128 after manufacture or use.

The following subject matter of this paragraph characterizes example 48of the present disclosure, wherein example 48 also includes the subjectmatter according to any one of examples 28 to 47, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises receiving information descriptive of the targetfluence and the target irradiance.

The target fluence and the target irradiance may be determined accordingto Eq. 1 and 2, experiment, modelling, type of material at surface 128,and type and/or amount of material to be removed from surface 128. Theinformation descriptive of the target fluence and the target irradiancemay include the value of the target fluence, the value of the targetirradiance, and/or operation parameters used to calculate the targetfluence and the target irradiance using Eq. 1 and 2. The informationreceived may be used to scan laser beam 120 in scan regions 136 with thetarget fluence and the target irradiance.

The following subject matter of this paragraph characterizes example 49of the present disclosure, wherein example 49 also includes the subjectmatter according to any one of examples 28 to 48, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises determining the target fluence and the targetirradiance based upon a received ablation depth.

The received ablation depth may be used to determine the target fluenceand the target irradiance based upon the type and/or amount of materialto be ablated, the optical absorbance of the material to be ablated, andthe laser wavelength. The relation between ablation depth and targetfluence and/or target irradiance may be determined by modelling and/orexperiment.

The following subject matter of this paragraph characterizes example 50of the present disclosure, wherein example 50 also includes the subjectmatter according to any one of examples 28 to 49, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, the target fluence is, for each one of scan regions 136, thelaser-beam average power divided by a product of the scan width and thetraverse scan speed. The target irradiance is, for each one of scanregions 136, the laser-beam average power divided by a product of thelaser pulse repetition rate, the laser pulse width, and the laser-beamspot area.

The target fluence and the target irradiance may be calculated accordingto Eq. 1 and 2. Using the same target fluence and target irradiance foreach of scan regions 136 facilitates uniform ablation across area 130.

The following subject matter of this paragraph characterizes example 51of the present disclosure, wherein example 51 also includes the subjectmatter according to any one of examples 28 to 50, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, laser beam 120 is configured to ablate area 130 of surface128 when laser beam 120 is applied along a nominal scan width with thetarget fluence and the target irradiance. The target fluence is anominal laser-beam average power divided by a product of the nominalscan width and a nominal traverse scan speed. The target irradiance isthe nominal laser-beam average power divided by a product of a nominallaser pulse repetition rate, a nominal laser pulse width, and a nominallaser-beam spot area.

Selection of a nominal scan width, a target fluence, and a targetirradiance may provide sufficient information to determine a nominallaser-beam average power, a nominal traverse scan speed, a nominal laserpulse repetition rate, a nominal laser pulse width, and/or a nominallaser-beam spot area. Alternatively, the nominal parameters may definethe target fluence and target irradiance. Selection of nominal scanwidth, target fluence, and/or target irradiance may be useful to tunelaser ablation system 100 to ablate different materials (the material tobe removed) and/or to preserve different materials (of surface 128) asmay be present on various workpieces 124.

The following subject matter of this paragraph characterizes example 52of the present disclosure, wherein example 52 also includes the subjectmatter according to any one of examples 28 to 51, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises determining a maximum scan width that is a maximumaverage power of laser beam 120 divided by a product of the targetfluence and a maximum traverse scan speed.

Maximum scan width may be determined by target fluence, the maximumaverage power of laser beam 120 (which also may be referred to asmaximum laser-beam average power), and the maximum traverse scan speed.The maximum average power of laser beam 120 may be limited by laser 102operation limits. The maximum traverse scan speed may be limited bymechanical limits of laser-positioning apparatus 106. The maximum scanwidth, as determined, may be used to qualify area 130 for the potentialfor ablation, to divide area 130 into separate subareas with no scanwidth 140 greater than the maximum scan width, and/or to section area130 into scan regions 136 that each have scan width 140 that is lessthan or equal to the maximum scan width.

The following subject matter of this paragraph characterizes example 53of the present disclosure, wherein example 53 also includes the subjectmatter according to any one of examples 28 to 52, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area is performed at least partially concurrently withscanning area 130 of surface 128.

Determining operation parameters (e.g., traverse scan speed, laser-beamaverage power, laser pulse repetition rate, laser pulse width, andlaser-beam spot area) may be performed during scanning of scan regions136. Before scanning an individual one of scan regions 136, operationparameters for that individual one of scan regions 136 are determined.Determining operation parameters for one of scan regions 136 is aprerequisite only for scanning that one of scan regions 136. Determiningoperation parameters may be done for one of scan regions 136 at a time(e.g., just prior to beginning scanning for individual ones of scanregions 136 and/or as individual ones of scan regions 136 are receivedand/or determined). Determining operation parameters at least partiallyconcurrently with scanning permits dynamic changes of operationparameters and/or scan regions 136 during scanning. Additionally oralternatively, determining operation parameters at least partiallyconcurrently with scanning may overlap the computational overhead timeneeded to determine operation parameters with the movement of scanninghead 104, laser beam 120, and/or workpiece 124 during scanning, hence,increasing operational efficiency.

The following subject matter of this paragraph characterizes example 54of the present disclosure, wherein example 54 also includes the subjectmatter according to any one of examples 28 to 53, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, according tomethod 200, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises determining the traverse scan speed inmultiplicative inverse relation to scan width 140 for each one of scanregions 136 when scan width 140 is greater than or equal to a firstcritical scan width.

For scan regions 136 in which scan width 140 is greater than or equal tothe first critical scan width (e.g., S₁ in FIG. 3), target fluence maybe achieved by selecting a traverse scan speed less than or equal to themaximum traverse scan speed. When scan width 140 is greater than orequal to the first critical scan width, target fluence may be achievedaccording to Eq. 2. The traverse scan speed may compensate for changesin scan width 140 in inverse proportion. Compensating changes in scanwidth 140 by inverse changes in traverse scan speed permits maintainingthe target fluence without changing operation parameters of laser 102.

The following subject matter of this paragraph characterizes example 55of the present disclosure, wherein example 55 also includes the subjectmatter according to any one of examples 28 to 54, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, according tomethod 200, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises equating the traverse scan speed to amaximum traverse scan speed and determining the laser pulse repetitionrate in proportion to scan width 140 for each one of scan regions 136when scan width 140 is less than a first critical scan width and greaterthan or equal to a second critical scan width. The first critical scanwidth is greater than the second critical scan width.

For scan regions 136 in which scan width 140 is less than the firstcritical scan width (e.g., S₁ in FIG. 3), target fluence may be achievedby selecting a traverse scan speed greater than the maximum traversescan speed. Smaller scan width 140 requires larger traverse scan speedto produce the same target fluence. If scan width 140 is small enough(i.e., less than the first critical scan width) to imply a traverse scanspeed greater than the maximum traverse scan speed, traverse scan speedmay be set to the maximum traverse scan speed and the laser-beam averagepower reduced to achieve the target fluence based on the maximumtraverse scan speed and scan width 140 that is less than the firstcritical scan width. The laser-beam average power may be reduced inproportion to the scan width 140 (according to Eq. 2) to achieve thetarget fluence. Laser-beam average power may be reduced in proportion tolaser pulse repetition rate while maintaining the target irradiance(according to Eq. 1). Hence, to achieve both the target fluence and thetarget irradiance, the laser pulse repetition rate may be reduced inproportion to scan width 140 while the traverse scan speed is at themaximum traverse scan speed. Scan regions 136 may have a second criticalscan width (e.g., S₂ in FIG. 3) below which this algorithm is notpractical, desired, or reliable.

The following subject matter of this paragraph characterizes example 56of the present disclosure, wherein example 56 also includes the subjectmatter according to any one of examples 28 to 55, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, according tomethod 200, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises equating the traverse scan speed to amaximum traverse scan speed, equating the laser pulse repetition rate toa minimum laser pulse repetition rate, and determining the laser pulsewidth in proportion to scan width 140 for each one of scan regions 136when scan width 140 is less than a second critical scan width andgreater than or equal to a third critical scan width. The secondcritical scan width is greater than the third critical scan width.

For scan regions 136 in which scan width 140 is less than the secondcritical scan width (e.g., S₂ in FIG. 3), target fluence may be achievedby selecting a traverse scan speed greater than the maximum traversescan speed and/or by selecting a traverse scan speed at the maximumtraverse scan speed and selecting a laser pulse repetition rate lessthan the minimum laser pulse repetition rate. Smaller scan width 140requires larger traverse scan speed to produce the same target fluenceand smaller laser pulse repetition to achieve the same target fluenceand target irradiance. If scan width 140 is small enough (i.e., lessthan the second critical scan width) to imply a traverse scan speed atthe maximum traverse scan speed and a laser pulse repetition rate lessthan the minimum laser pulse repetition rate, traverse scan speed may beset to the maximum traverse scan speed, laser pulse repetition rate maybe set to the minimum laser pulse repetition rate, and the laser-beamaverage power reduced to achieve the target fluence based on the maximumtraverse scan speed and scan width 140 that is less than the secondcritical scan width. The laser-beam average power may be reduced inproportion to scan width 140 (according to Eq. 2) to achieve the targetfluence. Laser-beam average power may be reduced in proportion to laserpulse width while maintaining the target irradiance (according to Eq.1). Hence, to achieve both the target fluence and the target irradiance,the laser pulse width may be reduced in proportion to scan width 140while the traverse scan speed is at the maximum traverse scan speed andthe laser pulse repetition rate is at the minimum laser pulse repetitionrate. Scan regions 136 may have a third critical scan width (e.g., S₃ inFIG. 3) below which this algorithm is not practical, desired, orreliable.

The following subject matter of this paragraph characterizes example 57of the present disclosure, wherein example 57 also includes the subjectmatter according to any one of examples 28 to 56, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 3, according tomethod 200, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises equating the traverse scan speed to amaximum traverse scan speed, equating the laser pulse repetition rate toa minimum laser pulse repetition rate, equating the laser pulse width toa minimum laser pulse width, and determining the laser-beam spot area inproportion to scan width 140 for each one of scan regions 136 when scanwidth 140 is less than a third critical scan width.

For scan regions 136 in which scan width 140 is less than the thirdcritical scan width (e.g., S₃ in FIG. 3), target fluence may be achievedby selecting a traverse scan speed greater than the maximum traversescan speed, by selecting a traverse scan speed at the maximum traversescan speed and selecting a laser pulse repetition rate less than theminimum laser pulse repetition rate, and/or by selecting a traverse scanspeed at the maximum traverse scan speed, selecting a laser pulserepetition rate at the minimum laser pulse repetition rate, andselecting a laser pulse width less than the minimum laser pulse width.Smaller scan width 140 requires larger traverse scan speed to producethe same target fluence, smaller laser pulse repetition to achieve thesame target fluence and target irradiance, and smaller laser pulse widthto achieve the same target fluence and target irradiance. If scan width140 is small enough (i.e., less than the third critical scan width) toimply a traverse scan speed at the maximum traverse scan speed, a laserpulse repetition rate at the minimum laser pulse repetition rate, and alaser pulse width less than the minimum laser pulse width, traverse scanspeed may be set to the maximum traverse scan speed, laser pulserepetition rate may be set to the minimum laser pulse repetition rate,laser pulse width may be set to the minimum laser pulse width, and thelaser-beam average power reduced to achieve the target fluence based onthe maximum traverse scan speed and scan width 140 that is less than thethird critical scan width. The laser-beam average power may be reducedin proportion to scan width 140 (according to Eq. 2) to achieve thetarget fluence. Laser-beam average power may be reduced in proportion tolaser-beam spot area while maintaining the target irradiance (accordingto Eq. 1). Hence, to achieve both the target fluence and the targetirradiance, the laser-beam spot area may be reduced in proportion toscan width 140 while the traverse scan speed is at the maximum traversescan speed, the laser pulse repetition rate is at the minimum laserpulse repetition rate, and the laser pulse width is at the minimum laserpulse width. Scan regions 136 may have a fourth critical scan width(e.g., S₄ in FIG. 3) below which this algorithm is not practical,desired, or reliable.

The following subject matter of this paragraph characterizes example 58of the present disclosure, wherein example 58 also includes the subjectmatter according to any one of examples 28 to 57, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, scanning area 130 of surface 128 comprises scanning laserbeam 120 at a raster scan speed across scan width 140 of each one ofscan regions 136.

Laser beam 120 is scanned a distance of scan width 140 across each oneof scan regions 136 and along scan width direction 144. Each one of scanregions 136 may have a different scan width 140. Laser beam 120 isscanned at a rate of the raster scan speed. The raster scan speed isfast relative to the traverse scan speed (rate of change between scanregions 136 and/or along the traverse direction 146). Generally, theraster scan speed is much faster than the traverse scan speed such thatlaser beam 120 as it is scanned at raster scan speed may be treated as alaser sheet. For example, the raster scan speed may be greater than1,000 times the traverse scan speed. Scanning may include opticallyscanning laser beam 120 because optically scanning laser beam 120 isgenerally much faster than mechanically scanning laser beam 120.

The following subject matter of this paragraph characterizes example 59of the present disclosure, wherein example 59 also includes the subjectmatter according to example 58, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, method 200 further comprisesdetermining the raster scan speed to completely ablate each one of scanregions 136 while scanning area 130 of surface 128.

The raster scan speed may be determined according to the amount and/ortype of material to be ablated, the optical absorbance of the materialto be ablated, and the laser wavelength. Slower raster scan speeds maydeposit more energy into a small region of surface 128 (i.e., a regionthe size of the laser-beam spot area) in a shorter time than fasterraster scan speeds. Faster raster scan speeds may be beneficial toreduce thermal effects on the underlying material of surface 128 aslaser beam 120 ablates the overlying material. Faster raster scan speedsmay permit vapor and/or particulates (e.g., smoke) to dissipatesufficiently to reduce optical interference with laser beam 120(relative to slower raster scan speeds). Generally, the raster scanspeed is sufficiently fast to treat the scanned laser beam 120 as alaser sheet.

The following subject matter of this paragraph characterizes example 60of the present disclosure, wherein example 60 also includes the subjectmatter according to any one of examples 58 to 59, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, method 200further comprises determining the raster scan speed to be greater than aproduct of scan width 140 and the traverse scan speed divided by aneffective average diameter of the laser-beam spot area for each one ofscan regions 136.

The raster scan speed may be great enough that the entirety of each oneof scan regions 136 is scanned by laser beam 120 before laser beam 120is moved at traverse scan speed in traverse direction 146 the distanceof an effective average diameter of the laser-beam spot area. Scanningat such a raster scan speed provides for uniform coverage of scanregions 136 and area 130. The effective average diameter of laser-beamspot area is the diameter of a circle having the same area as thelaser-beam spot area. The laser-beam spot area may or may not have acircular profile.

The following subject matter of this paragraph characterizes example 61of the present disclosure, wherein example 61 also includes the subjectmatter according to any one of examples 58 to 60, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, the raster scan speed for scan regions 136 is greater than aproduct of a maximum scan width and a maximum traverse scan speeddivided by an effective average diameter of a minimum laser-beam spotarea.

The raster scan speed may be set to accommodate the maximum scan widthand the maximum traverse scan speed that may be achieved for a givenapparatus (such as laser ablation system 100). Such a raster scan speedmay be used for each of scan regions 136. Hence, the raster scan speeddoes not need to be changed between scan regions 136 to maintain thetarget fluence or target irradiance.

The following subject matter of this paragraph characterizes example 62of the present disclosure, wherein example 62 also includes the subjectmatter according to any one of examples 28 to 61, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, scan regions 136 of area 130 of surface 128 are contiguousso that area 130 is continuous.

Scan regions 136 are contiguous with each other, i.e., neighboring scanregions 136 touch, partially overlap, and/or connect with each other.With contiguous scan regions 136, laser beam 120 may be scanned from oneof scan regions 136 to the next of scan regions 136 in a continuousmotion, without needing to translate surface 128 relative to scanninghead 104 between scan regions 136. Hence, scanning contiguous scanregions 136 does not need to incur delay between scan regions 136 andconsequent inefficiency of ablation of area 130. Contiguous scan regions136 provide for area 130 that is continuous and that may becharacterized by having a single boundary to encompass all of scanregions 136. Area 130 that is continuous may have no internal voids orvacancies (regions not included in one of scan regions 136).

The following subject matter of this paragraph characterizes example 63of the present disclosure, wherein example 63 also includes the subjectmatter according to any one of examples 28 to 62, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, area 130 of surface 128 consists of scan regions 136.

Area 130 may comprise scan regions 136, may consist essentially of scanregions 136, and may comprise only scan regions 136. Scan regions 136may be derived by sectioning area 130 such that each of scan regions 136is a portion of area 130.

The following subject matter of this paragraph characterizes example 64of the present disclosure, wherein example 64 also includes the subjectmatter according to any one of examples 28 to 63, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, sequentiallyscanning, across scan width 140, each one of scan regions 136 of area130 with laser beam 120 at the target fluence and the target irradiance,comprises scanning laser beam 120 across area 130 of surface 128 withscan spacing 148 separating scanning head 104 from area 130 of surface128.

Scan spacing 148 between scanning head 104 and area 130 of surface 128may provide clearance and/or avoid contact between scanning head 104 andsurface 128. Scan spacing 148 may be at focal point of laser beam 120(if laser beam 120 has a focal point outside of scanning head 104)and/or may function to establish the laser-beam spot area as laser beam120 is scanned across area 130.

The following subject matter of this paragraph characterizes example 65of the present disclosure, wherein example 65 also includes the subjectmatter according to example 64, above. Referring generally to FIGS. 1-3and particularly to, e.g., FIG. 4, according to method 200, scan spacing148, separating scanning head 104 from area 130 of surface 128, issubstantially constant within each one of scan regions 136.

Substantially constant (or uniform) scan spacing 148 within one of scanregions 136 may establish a substantially constant (or uniform)laser-beam spot area in that one of scan regions 136. For each one ofscan regions 136, scan spacing 148 may be substantially constant (oruniform), though different ones of scan regions 136 may be scanned withdifferent scan spacing 148 values. Scan spacing 148 (and hence possiblythe laser-beam spot area) may be optimized for each one of scan regions136 independently.

The following subject matter of this paragraph characterizes example 66of the present disclosure, wherein example 66 also includes the subjectmatter according to any one of examples 64 to 65, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, scan spacing 148, separating scanning head 104 from area 130of surface 128, is substantially constant for all scan regions 136.

Scan spacing 148 may not vary between scan regions 136, which mayfacilitate transitions between scan regions 136 without translation ofsurface 128 relative to scanning head 104. Substantially constant (oruniform) scan spacing 148 for all scan regions 136 may not precludeadjustment of laser-beam spot area. The laser-beam spot area may bevaried as necessary or desired by adjusting the focal distance of laserbeam 120 from scanning head 104.

The following subject matter of this paragraph characterizes example 67of the present disclosure, wherein example 67 also includes the subjectmatter according to any one of examples 28 to 66, above. Referringgenerally to FIGS. 1-3 and particularly to, e.g., FIG. 4, according tomethod 200, sequentially scanning, across scan width 140, each one ofscan regions 136 of area 130 with laser beam 120 at the target fluenceand the target irradiance, comprises scanning laser beam 120 across area130 of surface 128 with an angle of incidence substantially normal toeach one of scan regions 136.

Scanning each of scan regions 136 at a perpendicular (normal) angle ofincidence may provide for effective ablation in scan regions 136. Laserbeam 120 may have higher (or maximum) target irradiance when laser beam120 is oriented normal to surface 128. If laser beam 120 impingessurface 128 at an angle significantly different from normal(perpendicular), the spot of laser beam 120 may distort and becomelarger (thus reducing target irradiance). As used herein, a normal angleof incidence is approximately perpendicular to surface 128 (at about90°, e.g., within the range of 80°-90°).

Examples of the present disclosure may be described in the context ofaircraft manufacturing and service method 1100 as shown in FIG. 5 andaircraft 1102 as shown in FIG. 6. During pre-production, illustrativemethod 1100 may include specification and design (block 1104) ofaircraft 1102 and material procurement (block 1106). During production,component and subassembly manufacturing (block 1108) and systemintegration (block 1110) of aircraft 1102 may take place. Thereafter,aircraft 1102 may go through certification and delivery (block 1112) tobe placed in service (block 1114). While in service, aircraft 1102 maybe scheduled for routine maintenance and service (block 1116). Routinemaintenance and service may include modification, reconfiguration,refurbishment, etc. of one or more systems of aircraft 1102.

Each of the processes of illustrative method 1100 may be performed orcarried out by a system integrator, a third party, and/or an operator(e.g., a customer). For the purposes of this description, a systemintegrator may include, without limitation, any number of aircraftmanufacturers and major-system subcontractors; a third party mayinclude, without limitation, any number of vendors, subcontractors, andsuppliers; and an operator may be an airline, leasing company, militaryentity, service organization, and so on.

As shown in FIG. 6, aircraft 1102 produced by illustrative method 1100may include airframe 1118 with a plurality of high-level systems 1120and interior 1122. Examples of high-level systems 1120 include one ormore of propulsion system 1124, electrical system 1126, hydraulic system1128, and environmental system 1130. Any number of other systems may beincluded. Although an aerospace example is shown, the principlesdisclosed herein may be applied to other industries, such as theautomotive industry. Accordingly, in addition to aircraft 1102, theprinciples disclosed herein may apply to other vehicles, e.g., landvehicles, marine vehicles, space vehicles, etc.

Apparatus(es) and method(s) shown or described herein may be employedduring any one or more of the stages of the manufacturing and servicemethod 1100. For example, components or subassemblies corresponding tocomponent and subassembly manufacturing (block 1108) may be fabricatedor manufactured in a manner similar to components or subassembliesproduced while aircraft 1102 is in service (block 1114). Also, one ormore examples of the apparatus(es), method(s), or combination thereofmay be utilized during production stages 1108 and 1110, for example, bysubstantially expediting assembly of or reducing the cost of aircraft1102. Similarly, one or more examples of the apparatus or methodrealizations, or a combination thereof, may be utilized, for example andwithout limitation, while aircraft 1102 is in service (block 1114)and/or during maintenance and service (block 1116).

Different examples of the apparatus(es) and method(s) disclosed hereininclude a variety of components, features, and functionalities. Itshould be understood that the various examples of the apparatus(es) andmethod(s) disclosed herein may include any of the components, features,and functionalities of any of the other examples of the apparatus(es)and method(s) disclosed herein in any combination, and all of suchpossibilities are intended to be within the scope of the presentdisclosure.

Many modifications of examples set forth herein will come to mind to oneskilled in the art to which the present disclosure pertains having thebenefit of the teachings presented in the foregoing descriptions and theassociated drawings.

Therefore, it is to be understood that the present disclosure is not tobe limited to the specific examples illustrated and that modificationsand other examples are intended to be included within the scope of theappended claims. Moreover, although the foregoing description and theassociated drawings describe examples of the present disclosure in thecontext of certain illustrative combinations of elements and/orfunctions, it should be appreciated that different combinations ofelements and/or functions may be provided by alternative implementationswithout departing from the scope of the appended claims. Accordingly,parenthetical reference numerals in the appended claims are presentedfor illustrative purposes only and are not intended to limit the scopeof the claimed subject matter to the specific examples provided in thepresent disclosure.

1. A laser ablation system (100), comprising: a laser (102), configuredto emit a laser beam (120); a scanning head (104), configured to deliverthe laser beam (120), emitted by the laser (102), onto a surface (128);a laser-positioning apparatus (106), configured to adjust relativepositions of the surface (128) and the scanning head (104); and acontroller (110), programmed: to determine a traverse scan speed, alaser-beam average power, a laser pulse repetition rate, a laser pulsewidth, and a laser-beam spot area for each one of scan regions (136) ofan area (130) of the surface (128), wherein: the traverse scan speed,the laser-beam average power, the laser pulse repetition rate, the laserpulse width, and the laser-beam spot area, corresponding to any one ofthe scan regions (136), produce a target fluence and a target irradianceof the laser beam (120), the scan regions (136) are arranged so that allof the area (130) of the surface (128) is scannable with the laser beam(120), each one of the scan regions (136) has a scan width (140), andthe scan width (140) of at least one of the scan regions (136) isdifferent from the scan width (140) of another one of the scan regions(136); and to scan the area (130) of the surface (128) with the laserbeam (120) at the target fluence and the target irradiance by scanningeach one of the scan regions (136) at the traverse scan speed,corresponding to that particular one of the scan regions (136), andacross the scan width (140), corresponding to that particular one of thescan regions (136), wherein the laser beam (120) has: the laser-beamaverage power, corresponding to that particular one of the scan regions(136), the laser pulse repetition rate, corresponding to that particularone of the scan regions (136), the laser pulse width, corresponding tothat particular one of the scan regions (136), and and the laser-beamspot area, corresponding to that particular one of the scan regions(136). 2-6. (canceled)
 7. The laser ablation system (100) according toclaim 1, wherein: the target fluence is, for each one of the scanregions (136), the laser-beam average power divided by a product of thescan width and the traverse scan speed, and the target irradiance is,for each one of the scan regions (136), the laser-beam average powerdivided by a product of the laser pulse repetition rate, the laser pulsewidth, and the laser-beam spot area.
 8. (canceled)
 9. The laser ablationsystem (100) according to claim 1, wherein the controller (110) isconfigured to receive the scan regions (136) of the area (130) of thesurface (128).
 10. The laser ablation system (100) according to claim 1,wherein the controller (110) is programmed to determine the scan regions(136) of the area (130) of the surface (128) based upon a virtual modelof the surface (128). 11-18. (canceled)
 19. The laser ablation system(100) according to claim 1, wherein the controller (110) is programmedto determine the traverse scan speed, the laser-beam average power, thelaser pulse repetition rate, the laser pulse width, and the laser-beamspot area by equating the traverse scan speed to a maximum traverse scanspeed and determining the laser pulse repetition rate in proportion tothe scan width (140) for each one of the scan regions (136) when thescan width (140) is less than a first critical scan width and greaterthan or equal to a second critical scan width, wherein the firstcritical scan width is greater than the second critical scan width. 20.The laser ablation system (100) according to claim 1, wherein thecontroller (110) is programmed to determine the traverse scan speed, thelaser-beam average power, the laser pulse repetition rate, the laserpulse width, and the laser-beam spot area by equating the traverse scanspeed to a maximum traverse scan speed, equating the laser pulserepetition rate to a minimum laser pulse repetition rate, anddetermining the laser pulse width in proportion to the scan width (140)for each one of the scan regions (136) when the scan width (140) is lessthan a second critical scan width and greater than or equal to a thirdcritical scan width, wherein the second critical scan width is greaterthan the third critical scan width.
 21. The laser ablation system (100)according to claim 1, wherein the controller (110) is programmed todetermine the traverse scan speed, the laser-beam average power, thelaser pulse repetition rate, the laser pulse width, and the laser-beamspot area by equating the traverse scan speed to a maximum traverse scanspeed, equating the laser pulse repetition rate to a minimum laser pulserepetition rate, equating the laser pulse width to a minimum laser pulsewidth, and determining the laser-beam spot area in proportion to thescan width (140) for each one of the scan regions (136) when the scanwidth (140) is less than a third critical scan width. 22-27. (canceled)28. A method (200) of using a laser ablation system (100) to clean anarea (130) of a surface (128) with a laser beam (120), having a targetfluence and a target irradiance, the area (130) comprising scan regions(136), each having a scan width (140), the method comprising:determining a traverse scan speed, a laser-beam average power, a laserpulse repetition rate, a laser pulse width, and a laser-beam spot areaof the laser beam (120) for each one of the scan regions (136) toachieve the target fluence and the target irradiance of the laser beam(120) when scanning each one of the scan regions (136) with the laserbeam (120), wherein the scan width (140) of at least one of the scanregions (136) is different from the scan width (140) of another one ofthe scan regions (136); and sequentially scanning, across the scan width(140), each one of the scan regions (136) of the area (130) with thelaser beam (120) at the target fluence and the target irradiance. 29.The method (200) according to claim 28, wherein when the scan width(140) of at least one of the scan regions (136) is different from thescan width (140) of another one of the scan regions (136), at least oneof the traverse scan speed, the laser-beam average power, the laserpulse repetition rate, the laser pulse width, or the laser-beam spotarea of the laser beam (120) for at least the one of the scan regions(136) is different from at least one of the traverse scan speed, thelaser-beam average power, the laser pulse repetition rate, the laserpulse width, or the laser-beam spot area of the laser beam (120) for theother one of the scan regions (136).
 30. (canceled)
 31. The method (200)according to claim 28, wherein: the laser beam (120) has an initiallaser-beam average power, the scan regions (136) comprise an adaptedscan region, determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area for each one of the scan regions (136) comprisesdetermining that a projected traverse scan speed for the adapted scanregion is greater than a maximum traverse scan speed, the projectedtraverse scan speed for the adapted scan region is the initiallaser-beam average power divided by a product of the scan width (140) ofthe adapted scan region and the target fluence, and the method (200)further comprises determining an adapted laser-beam average power thatis a product of the target fluence, the scan width (140) of the adaptedscan region, and the maximum traverse scan speed.
 32. The method (200)according to claim 31, wherein: the laser pulse repetition rate of theadapted scan region is the adapted laser-beam average power divided by aproduct of the target irradiance, the laser pulse width for the adaptedscan region, and the laser-beam spot area for the adapted scan region;and scanning the area (130) of the surface (128) comprises scanning theadapted scan region at the maximum traverse scan speed across the scanwidth (140) of the adapted scan region while the laser beam (120) hasthe adapted laser-beam average power, the laser pulse repetition ratefor the adapted scan region, the laser pulse width for the adapted scanregion, and the laser-beam spot area for the adapted scan region. 33.The method (200) according to claim 31, wherein: determining thetraverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, and the laser-beam spot area foreach one of the scan regions (136) comprises determining that aprojected laser pulse repetition rate for the adapted scan region isless than a minimum laser pulse repetition rate, and the projected laserpulse repetition rate for the adapted scan region is the adaptedlaser-beam average power divided by a product of the target irradiance,the laser pulse width for the adapted scan region, and the laser-beamspot area for the adapted scan region.
 34. The method (200) according toclaim 33, wherein: the laser pulse width for the adapted scan region isthe adapted laser-beam average power divided by a product of the targetirradiance, the minimum laser pulse repetition rate, and the laser-beamspot area for the adapted scan region; and scanning the area (130) ofthe surface (128) comprises scanning the adapted scan region at themaximum traverse scan speed across the scan width (140) of the adaptedscan region while the laser beam (120) has the adapted laser-beamaverage power, the minimum laser pulse repetition rate, the laser pulsewidth for the adapted scan region, and the laser-beam spot area for theadapted scan region.
 35. The method (200) according to claim 33,wherein: determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area for each one of the scan regions (136) comprisesdetermining that a projected laser pulse width for the adapted scanregion is less than a minimum laser pulse width; the projected laserpulse width for the adapted scan region is the adapted laser-beamaverage power divided by a product of the target irradiance, the minimumlaser pulse repetition rate, and the laser-beam spot area for theadapted scan region; the laser-beam spot area for the adapted scanregion is the adapted laser-beam average power divided by a product ofthe target irradiance, the minimum laser pulse repetition rate, and theminimum laser pulse width; and scanning the area (130) of the surface(128) comprises scanning the adapted scan region at the maximum traversescan speed across the scan width (140) of the adapted scan region whilethe laser beam (120) has the adapted laser-beam average power, theminimum laser pulse repetition rate, the minimum laser pulse width, andthe laser-beam spot area for the adapted scan region. 36-52. (canceled)53. The method (200) according to claim 28, wherein determining thetraverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, and the laser-beam spot area isperformed at least partially concurrently with scanning the area (130)of the surface (128).
 54. The method (200) according to claim 28,wherein determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises determining the traverse scan speed inmultiplicative inverse relation to the scan width (140) for each one ofthe scan regions (136) when the scan width (140) is greater than orequal to a first critical scan width.
 55. The method (200) according toclaim 28, wherein: determining the traverse scan speed, the laser-beamaverage power, the laser pulse repetition rate, the laser pulse width,and the laser-beam spot area comprises equating the traverse scan speedto a maximum traverse scan speed and determining the laser pulserepetition rate in proportion to the scan width (140) for each one ofthe scan regions (136) when the scan width (140) is less than a firstcritical scan width and greater than or equal to a second critical scanwidth; and the first critical scan width is greater than the secondcritical scan width.
 56. The method (200) according to claim 28,wherein: determining the traverse scan speed, the laser-beam averagepower, the laser pulse repetition rate, the laser pulse width, and thelaser-beam spot area comprises equating the traverse scan speed to amaximum traverse scan speed, equating the laser pulse repetition rate toa minimum laser pulse repetition rate, and determining the laser pulsewidth in proportion to the scan width (140) for each one of the scanregions (136) when the scan width (140) is less than a second criticalscan width and greater than or equal to a third critical scan width; andthe second critical scan width is greater than the third critical scanwidth.
 57. The method (200) according to claim 28, wherein determiningthe traverse scan speed, the laser-beam average power, the laser pulserepetition rate, the laser pulse width, and the laser-beam spot areacomprises equating the traverse scan speed to a maximum traverse scanspeed, equating the laser pulse repetition rate to a minimum laser pulserepetition rate, equating the laser pulse width to a minimum laser pulsewidth, and determining the laser-beam spot area in proportion to thescan width (140) for each one of the scan regions (136) when the scanwidth (140) is less than a third critical scan width. 58-63. (canceled)64. The method (200) according to claim 28, wherein sequentiallyscanning, across the scan width (140), each one of the scan regions(136) of the area (130) with the laser beam (120) at the target fluenceand the target irradiance, comprises scanning the laser beam (120)across the area (130) of the surface (128) with a scan spacing (148)separating a scanning head (104) from the area (130) of the surface(128). 65-67. (canceled)